In comparing the difference between Einstein’s brain and a brain of Einsteins, it is important to realize that these two cerebral structures are so different that it is nearly impossible to see a “brain” of Einsteins as being as brain at all. The most significant characteristic of a human brain (or any brain for that matter) is that macro, complicated behavior can emerge as a result of billions of smaller interactions between neurons that follow very simple rules. If a neuron is given a specific stimulation at its pre-synapses, it will always send the same information to its post-synapses; there is no decision making involved. In contrast, if a neuron were to instead have the properties of an entire Einstein brain, each individual neuron would have sentience and have the ability to make its own decision. As a result of this, each Einstein brain can do whatever it wants with the stimulation it receives from other Einsteins, and its output is not predictable.
A good analogy for this brain of sentient entities is a community with a purely democratic system of government. While a purely democratic system of government may sound like a good idea in theory, such a government would be inefficient and unable to cope with the demands for adaptation in this world. The same is true of a brain that operates on a network of billion of Einstein brains. Each Einstein would have his own say in the mental processes that occur in the bigger a brain, and because of this it is unlikely that the high parallel computing power that the brain is famous for will ever get achieved. Instead, each Einstein will try to convince the other Einsteins of what should be done and the reasons for doing so. If it were a brain where each neuron is someone’s brain that is less stubborn than Einstein this problem would not be so pronounced. Image having billions Einsteins who spend 30 years trying to disprove an idea that most other renowned physicists have embraced, and image these Einsteins trying to make a decision together. If there was a lion running towards this entity of Einsteins, the decision processes of all the individual Einsteins would not be processes fast enough to save the entity.
However, while it is evident that Einsteins in conflict will never get anything done, what if each Einstein was working towards a common goal and that all the Einsteins were synch in their objective. In this case the brain of Einsteins would be a force to be reckoned with. It would be having a two dimensional array as opposed to a one dimensional array and the computing power would be much greater than that of an individual brain. One only has to look at the Borg race from Star Trek to see the powers that a network of connected individuals have as long as they are drones and working for a common goal without the ability to make their own personal decisions.